bug#56691: outline-minor-mode displays navigation arrow buttons as emojis

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: luangruo@yahoo.com,  rpluim@gmail.com,  56691@debbugs.gnu.org,
>   hello@paulwrankin.com
> Date: Mon, 01 Aug 2022 14:36:41 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Why should it care about a specific font?  And how will you obtain a
> > font in these cases to begin with?  Fonts are extremely platform- and
> > user-configuration-dependent, so I see no reason to try to deal with
> > them.
> 
> I don't follow you at all here.
> 
> We've got an emoji to display, so we look up what font Emacs wants to
> display it with, and then we check whether that font is an emoji font or
> not (by checking that it's a colour font).

I thought we agreed this was not a good idea?  First, it can be slow,
if there are no such fonts.  Next, the fonts might be set up so that a
B&W font is selected while a color font does exist.  Etc. etc. -- it
looks like we gain very little or nothing at all for all this trouble.

Faced with these complications, I thought we decided just to test for
the _potential_ of displaying color Emoji, and leave it to the user to
set their systems so that the potential is realized, or customize
Emacs to disable color Emoji.  That sounds much easier, more reliable,
and on top of that can be extended to TTY frames that are capable of
displaying color Emoji, whereas what you propose isn't.